Cathode



p l 1936. w. W. EITEL All. 2,

CATHODE Filed April 17, 1934 l I /Z M 1 4 Hi IN V EN TORS.

WILL/AM w. f/TEL. JACK McCULLOUGH.

Patented Apr. 14, 1936 UNITED STATES PATENT OFFICE CATHODE William W.Eitel and Jack McCullough, San Bruno, Calif., assignors to Heintz &Kaufman, Ltd., San Francisco, Calif., a corporation of Nevada.

Application April 17, 1934, Serial No. 720,941

2 Claims. (01. 250 27.5)

Our invention relates to cathodes for thermior two kilowatts, areusually provided, due to the onic devices, and particularly to the formof such heavy currents handled, with a plurality of cathodes. cathodesor filaments connected together in Among the objects of our inventionare: to parallel. An example of such a construction, and

provide an improved mounting for multiple filaone which is extensivelyused, is illustrated in ments of thermionic devices; to provide a mul-Figure 2 of the drawin t e ve V yp tiple filament construction whichdistributes ments being indicated by the reference numeral the electronflow therefrom more uniformly over 2. The free ends of the filaments areusually the anode surface; to provide a cathode construcsecured to a par of Spreader bars 3 Which a welded to the ends of leads 4 supported bythe tion in which the heat drain from portions of the filaments issubstantially eliminated; to prostem 6 of the tube. The shape of t e pvide an improved cathode onstruction which bars varies considerably indifi'erent designs of produces relatively greater electron emission thantube, some manufacturers preferring the Straight similar cathodes inpresent use; and to provide a yp as illustrated, and Others preferring Usimplified and compacted multiple cathode conaped A ta d e150 Supportedy the struction for thermionic devices. stem a point jac nt t e ads e ed p- Other objects of our invention will be apparent Wardly and iprovided heal the p thereof W or will be specifically pointed out in thedescripsuitable means for engagin the hights 0f the tion forming a partof this specification, but we filaments, Which means y Conveniently be ado not limit ourselves to the embodiment of the p of resilient arms 8for tehsioning the fi ainvention herein described, as various forms maymerits a d p v \With hooked portions 9 for be adopted within the scopeof the claims. a g the tS er o Referring to the drawing: t It has beenobserved, under actual working Figure 1 is a perspective view showingthe conditions, that when filaments mounted in this improved cathode ofour invention as incorpofashion are heated, these Portions of each ratedin a space discharge device and showing ment adjace t t e Spreader bars,as arbitrarily its relationship to other electrodes mounted indicated bythe dimension A in u e l not therein. Parts of the view are broken awayto be raised to the Same t p ure s t redisclose the construction moreclearly. mainder of the filament. This is due to heat Figure 2 is aperspective view of the generally drainage from these portions of the fia y practiced method of mounting multiple filaments. the Spreader barsand the terminals- It w In broad terms, our invention comprises ththerefore, that maximum electron emission is combination, in anelectrical discharge device t p oeu ab e from filaments mounted in thehaving, preferably, a substantially tubular anode; manner described. atubular shaped control electrode comprising a Still another detrimentalfeature of such a plurality, of spaced vertically disposed conductors,construction lies in the fact that due to the close a cathode supportcomprising, preferably, a cyrelative spacing of each filament adjacentthe lindrical standard in axial alinement with the bight thereof, thatarea of the anode nearest the anodeand control electrode, and a pair ofspaced bight will receive a concentrated electron bomcathode terminalsdisposed adjacent the standbardment, while proportionately few electronsard, of a cathode comprising a pair of filaments will fall on the areasof the anode farthest re-. secured to each other, and to a terminal, atthe moved from the bights. In most instances, the ends thereof, thefilaments diverging with rep w r b n h n y h tube is such that spect toeach other from the terminals to a point this bombardment may be ofsufiicient magnitude equivalent to substantially half of the length tocause serious overheating of the anode in the of the filaments, providedwith bights at this areas subj c to the concentrated bombardpoint, andspaced apart a distance corresponding ment, with accompanyingdetrimental effect 011 with the spacing of the terminals, so that thethe eiflcient operation of the tube.

filaments are disposed in angular relationship We have, by the provisionof an improved with each other and are symmetrical in vertical planesdisplaced ninety degrees about a horizontal plane passing midway betweenthe terminals and the bights.

' A great majority of the thermionic tubes designed for operation atpowers of the order of one defects to a considerable degree, byproviding for an increase in the electron emission from the cathode, bysubstantially reducing the heat drain at the attachment points andthereby, by such provision, creating a tube capable of sumounting formultiple filaments, obviated these perior performance. Furthermore, wehave caused the filament wires to converge at the attachment points sothat one wire will help heat the other. We have also succeeded indistributing the electron emission from the cathode more uniformly overthe anode surface which permits greater heat dissipation by thiselectrode than is possible were it operating with the type of cathodegenerally used.

In greater detail, the preferred form of the improved cathode of ourinvention, and its relationship to other electrodes in a space dischargetube, is shown in Figure 1, in which the stem 6 is provided with thestandard I and theterminals 4, the standard, at its upper end, beingprovided with the resilient arms 8 formed with thebight engaging hooks9. An anode H and a control electrode 12 are shown surrounding thecathode.

The spreader bars 3 of the previously described construction have beendispensed with and the filaments 2 have been brought together at theirends and anchored by welding directly. to the ends of the terminals4.The terminals are preferably spaced apart a distance corresponding tothe spacing of the hooks 9 so that each filament is disposed in relationto the other at the same angle as the angle of the legs of each filamentbetween the bightand the terminals thereof. It will thus be seen thatthecombined filaments are symmetrical in vertical planes displacedninety degrees with a horizontal plane passing midway between the bightsand the terminals.

Due to the elimination of the spreader bars the heat drain from theanchored ends of the filaments has been greatly reduced, in factobservations of a cathode constructedin this manner, under actualworking conditions, failed to disclose a discernable portion of thefilaments that was not heated to emission temperature. This, it isbelieved, isdue to'the heat radiating from the closely adjacent portionsof the filaments near the terminals, assisting in raising thetemperature of each other to a degree corresponding to other parts ofthefilaments, and this together with the reduced heat drainage, providedby removal of the spreader bars, causes the filaments to be heated toemission temperature over their entire lengths between the terminals. Itis obvious, therefore, that due to the substantial elimination of thisundesirable heat drainage, the electron emission of thecathode, for agiven exciting current, is-considerably increased, which increase re.-fiects itself in improved performance of the tube.

Another desirable feature, created by the arrangement of the filamentsin this manner, is the symmetry of the cathode when it is viewedalternately from each end in positions rotatedninety degrees from eachother. This provides, at the filament terminals, a similar condition tothat existing at the bights thereof, in that the filaments are in thesame spaced relationship at the two points. Thus the concentration ofelectron flow from the cathode to the anode H is similar at both ends ofthe latter electrode and, as a result of this, more uniform distributionof electrons is obtained over the surface of the anode and it is capableof dissipating the heat generated more rapidly, consequently theelectrode is not likely to be overheated.

Still another desirable feature presents itself in that since thecathode assembly has been compacted, due to the removal of the spreaderbars, the diameter of the control electrode l2, and also the anode I I,may be considerably reduced. This may readily be seen by referring tothe drawing. The diameter of the smallest cylinder that could be placedabout the construction of Figure 2, is slightly greater than thediagonal distance between the ends of opposite spreader bars, while thediameter of a cylinder that would clear the construction of Figure 1, isslightly greater than the distance between the outer surfaces of theterminals. This distance, it will be seen, is considerably less than thediagonal distance referred to in respect to Figure 2. The elimination ofthe spreader bars and the rearrangement of the filaments are alsoinstrumental in reducing danger of arcing between grid and cathode.

The cathode just described permits the production of thermionic tubespossessing a higher degree of efficiency than was heretofore obtained intubes of this character, permits a reduction in size of the tubeelements, and due to its simplicity it may be constructed moreeconomically and expeditiously.

We claim:

1. The combination, in an electrical discharge device having an'anode, acontrol electrode and a cathode support contained therein, said supportcomprising a pair of spaced cathode terminals, a standard disposedadjacent said terminals and resilient arms mounted on said standard, ofa cathode comprising a pair of filaments joined together at their freeends and secured to said terminals, said filaments being looped oversaid resilient arms in spaced relationship, said spacing correspondingto substantially the spacing between the terminals.

2. The combination, in an electrical discharge device having a pluralityof cooperating electrodes mounted therein including a cathode support,of a cathode comprisinga plurality of filaments provided with bightssubstantially midway between their free ends, said bights adapted to besupported by said cathodesupport, a free end of each filament beingsecured to a free end of another filament in a plane substantiallyninety degrees out ofphase with a'plane passing through the bights ofthe filaments.

WILLIAM W. EITEL. JACK MCCULLOUGH.

